Field of the Invention
The present invention relates to the field of instrumentation for cryogenic systems.
Related Art
Instrumentation for cryogenic systems is a challenging problem that requires costly custom made electronics. The vast majority of commercially available active electronic components do not operate at temperatures below −50° C. This is due to several factors such as carrier freeze out, hot-carrier effects, and commercially available systems not being generally designed for low temperature operation.
Although the majority of commercial electronic systems operate above −50° C., there are a significant number of applications that need to operate at temperatures below −50° C., such as Liquid Natural Gas (LNG) storage and transportation, Magnetic Resonance Imaging (MRI), biology and physics experiments, superconducting magnets, cryogenic freezers, and several other industrial processes.
Currently, instrumentation and data acquisition for these systems is usually broken into two environments; with sensors in a cold part (e.g. a cryostat), and front-end and conditioning electronics outside at room temperature.
A cryostat is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various refrigeration methods, most commonly using a cryogenic fluid bath such as liquid helium. Hence it is usually assembled into a vessel, similar in construction to a vacuum flask or Dewar. Cryostats have numerous applications within science, engineering, and medicine.
Sensors may be attached to a device inside the cryostat and wires may connect the device to a data acquisition system outside the cryostat. In most cases, this is not an ideal solution due to several reasons, including electronic noise, heat loss into the cryostat, and increase of sealing complexity. Wires going out of the cryostat act like a heat sink, decreasing the efficiency of the cryostat in two ways; more energy is needed to keep the system cold, and coolant is lost through the feed through electric interface.
Furthermore, electrical signals coming from sensors inside the cryostat are only buffered and digitized outside the cryostat, thus increasing the number of wires passing out of the cryostat, and increasing the overall probability of failure due to a bad connection. In applications involving the potential for high voltages such as superconducting magnets, these high voltage wires are typically passing through a cryostat head, and sometimes they have to traverse a long path through cryogenic fluid, possibly passing through a transition region made of vapor where a dielectric breakdown constant is much lower. This can cause electrical discharges inside the cryostat, and result in damage to the system.